Product inventory monitoring

ABSTRACT

The present invention defines six unexpected benefits resulting from the automation of and improvements to inventory reconciliation and tank level monitoring at tank farms, terminals and refineries, commonly associated with refining and the transportation of, hydrocarbon fuels. In the implementation of an automated system for tank level monitoring and periodic inventory reconciliation, it has been discovered that both applications can be used to correctly identify maintenance needs and policy violations that were previously unable to be identified. The benefits include identification of thermal relief valve failure, transmix check valve failure, lock out/tag out failure, floating roof landing, and incorrect tank assignments.

CROSS REFERENCE TO RELATED APPLICATION

The present patent application is based upon and claims the benefit ofprovisional patent application No. 62/728,921 filed on Sep. 10, 2018.

BACKGROUND OF THE INVENTION

Inventory reconciliation is the process of comparing the expected amountof inventory (book inventory) against the physical inventory presentwithin tankage. The current process of inventory reconciliation usesbills of lading, pipeline/marine tickets and tank snapshots to calculatea physical inventory versus book inventory comparison. The improvedprocess calculates physical versus estimated book on an hourly basisusing available real-time instrumentation. These calculations areperformed over four rolling time periods (1-hour, 4-hour, 12 hours and24 hour) to catch potential large deviations in the short term andsmaller deviations in the long term. The following is evaluated for anygiven product tank at a terminal:

Physical Volume—Tank physical volume is captured from real-time tankgauge levels that are converted to gross standard (net) volume in thetank management system.

Rack Disposals—Rack meters are read from the lane presets to calculaterack disposals. The rack disposals are assigned to tanks based on themeter configuration in the accounting system.

Truck Offloads—Electronic bills of lading are used to calculate offloadvolume. Offloads are assigned to tanks based on the offloadconfiguration in the accounting system.

VRU Recovery—Rack gasoline throughput via rack meters is used with adefined recovery rate to estimate VRU recovery volume. The VRU recoveryis assigned to tanks based on configurations in the accounting system.

Butane Blending—Butane blending is accounted for by subtracting theinjection meter volume from the rack disposals. Butane blending isassigned to a tank on a per injector basis.

Pipeline/Marine Receipts/Deliveries—Pipeline and marine movements areaccounted for in one of two manners. Both require manual entry ofplanned movements into the accounting system to define the volume, flowrate and tank associated with a movement.

-   -   When possible, pipeline and marine meters are captured on a        real-time basis. The hourly delta volume of the pipeline or        marine meter is applied to the planned movements.    -   When physical meters are not available, the planned flow rate is        used to estimate the hourly planned movement. The start of the        planned movement is based on the tank flow rate crossing a        defined threshold. This improves the accuracy of the planned        movement since planned movements typically don't have fixed        start times.

Tank Transfers—Tank transfers are estimated based on a pair of manuallyentered planned movements and the defined flow rate as entered in theaccounting system. The start of the transfer is based on the tank flowrate crossing a defined threshold.

A deviation percent is calculated based on rack disposals from a giventank for each of the time periods. If a tank doesn't have enough rackdisposals for that time period, a minimum rack disposal volume isdefined to accommodate the accuracy of the tank gauge. This deviationpercent is compared to a variety of defined thresholds per time periodto determine if an alarm needs to be triggered. These thresholdsinclude:

-   -   Minimum physical—estimated book volume when a metered planned        movement is occurring.    -   Minimum physical—estimated book volume when a non-metered        planned movement is occurring.    -   Minimum physical—estimated book volume.    -   Deviation percent.

Alarms are disabled if a communication issue has occurred with the lanepresets or the tank management system.

When an alarm is triggered, a notification email is sent to theappropriate personnel to alert them to the issue, so they can analyzethe issue. If the alarm is related to a manually input planned movement,the personnel can modify the planned movement and recalculate the tankto correct the issue.

If an unusual event occurred causing the alarm, such as a tank waterdraw, meter providing or tank temperature issues, the personnel canenter a volume offset for the given hour and recalculate the tank.

Tank level monitoring is the process of remotely monitoring tank levelsand volumes in real-time for deviations from the expected level andvolume and providing immediate notification to appropriate personnelwhen a deviation outside set limits is detected. The following areevaluated for any given tank at a terminal:

-   -   Physical Volume and Level—Tank volume and level are captured        using real-time tank gauge levels that are converted to gross        standard (net) volume using a temperature compensation algorithm        in the tank management system.    -   Rack Loading—Rack meters are read from the lane presets to        determine rack loading events. Rack loading events are assigned        to tanks based on the meter definitions in the accounting        system.    -   Pipeline/Marine Receipts/Deliveries—Pipeline and marine        movements are accounted for using a custom form in the        accounting system. The form requires manual entry to define the        tank and the direction of the level change in the tank. The        start of the movement is based on the tank flow rate crossing a        defined threshold.    -   Level and Volume Deviation—Deviations are calculated utilizing a        custom calculation that determines when the level and volume of        a tank deviates from the expected level and volume following the        completion of the most recent rack loading event, or movement.        Alarms are declared under any one of three scenarios:    -   Tank level and volume increase or decrease outside a set limit.    -   Tank level and volume increase outside a set limit, during a        movement in which the tank level and volume is expected to        decrease.    -   Tank level and volume decrease outside a set limit, during a        movement in which the tank level and volume is expected to        increase.

When communication issues are detected between the product inventorysystem and the real-time tank management system, alarming is suppresseduntil the communication issue has been resolved. Instrumentation can bedeclared as disabled when maintenance work is being performed.

At some terminals, tanks are connected so they “float’ together. Volumesof inventory float out of each tank or into each tank. The individualtanks are grouped together for monitoring and are treated as a singletank. Typically, the alarming is done at the group level and theindividual tanks have alarming disabled. Any number of tanks can begrouped together. This feature is also used to show the physical versusthe estimated book inventory of a product level in grouped tanks.

When an alarm is triggered, a notification email is sent to theappropriate personnel to alert them to the issue so they can analyze theissue. If the alarm is related to a manually input planned movement thepersonnel can modify the planned movement and recalculate the tank tocorrect the issue. If an unusual event occurred causing the alarm, suchas tank water draw, meter providing or tank temperature issues, thepersonnel can enter a volume offset for the given hour and recalculatethe tank.

The systems installed to implement periodic inventory reconciliation andtank level monitoring have led to the discovery that the instrumentationcan be used to correctly identify maintenance needs and balanceviolations that were previously unable to be identified or would haverequired much longer periods of observation and troubleshooting tocorrectly identify.

BRIEF DESCRIPTION OF THE DRAWING

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

FIG. 1 is a graph that depicts a thermal relief failure.

FIG. 2 is a graph that depicts a check valve failure.

FIG. 3 is a graph that depicts a lock out/tag out failure.

FIG. 4 is a graph that depicts a tank roof landing.

FIG. 5 is a graph that depicts a tank roof landing bounce.

FIG. 6 is a graph that depicts a misdirected flow.

FIG. 7 is a graph that depicts a tank level decreasing due to truckloading, with no associated meter activity changes

FIG. 8 is a graph that depicts the level of a second tank that is notdecreasing, despite repeated requests to load trucks at the rack.

FIG. 9 is a graph that depicts an improperly seated valve.

FAILED THERMAL RELIEF VALVES

Referring now to FIG. 1, the first unexpected benefit disclosed by thevariations provided by the sensors involves the identification offailing thermal relief valves. A thermal relief valve is a temperaturevalve that will release and divert product to avoid pressure within thesystem exceeding safe limits. There are a number of thermal reliefvalves that cannot be tested because the product or the pipe location isnot safe. Testing is omitted and therefore, the only option is toreplace the valve if there is believed to be a failure. When a thermalrelief valve fails, it diverts product to the transmix tank rather thanthe destination. The transmix tank is a refuge tank which is a mixtureof all petroleum products at a terminal that will be sent back to therefinery for secondary refinement.

Thermal relief valves fail through normal wear and tear at theterminals. To protect against undetected failures, terminals arerequired to test the valves twice annually. There are, however,locations where the valves cannot be easily tested and failures may goundetected for long periods of time, in some cases years. Combining tankalarm information with planned movement entries provides data thatdetects when a product is misdirected through a failed thermal reliefvalve to the transmix tank. This action mitigates potential productrelease issues and tank over fills. Referring to FIG. 1 it can be seenthat, the first incident of a thermal relief valve failure appears to berecurring over multiple years prior to being identified. The secondinstance of a thermal relief valve failure has been occurring for lessthan a month. In the instance of FIG. 1, a thermal relief valve hadfailed and was diverting small amounts of product to the transmix tankrather than the finished product tank.

When a thermal relief valve fails in the open position, it will remainso until replaced. The failure of the thermal relief valve in FIG. 1 wasdiscovered by capturing a line from a transmix tank which indicated thewell level of the transmix tank was changing. This indicated thatproduct was flowing into the transmix tank during transport. The loss ona monthly basis was so small it would not have been identifiable at theend of the month reconciliation. By monitoring the level and volume ofall tanks, it can be determined that product is being diverted to animproper location or unexpected location.

Failed Check Valves

Referring now to FIG. 2, a failed check valve is discovered by using thetank monitoring system which shows a slow continuous loss of productvolume from the tank over an extended period. Initially this check isfor a transmix check valve failure. The product will flow back to theoil water separator when the transmix tank check valve fails. Normallythe check valve allows product to flow only from the oil water separatorto the transmix tank. A transmix check valve cannot be testedmechanically while it is live. It must be removed from the line andbench tested which requires a lock out and draining of tanks. Thisparticular event is difficult to identify in that product pumps from theoil water separator to the transmix tank. If the check valve fails, theproduct flows back to the oil water separator where it is then pumpedback to the transmix tank and this process continues. In the past, theonly way to identify this problem would be to physically notice the oilwater separator continuously running by hearing it running in the field.If the oil water separator pump were to fail, there would likely be anenvironmental spill as the oil water separator generally sits below atransmix tank. The pressure from the transmix tank would likely overflowthe oil water separator. Referring to FIG. 2, three such events havebeen continuously occurring. It can be seen that the transmix level ischanging as it is increasing and decreasing over distinct periods oftime.

Lock Out/Tag Out Integrity

Referring now to FIG. 3, one of the most critical tests at a fieldlocation is the application of lock out/tag out. Lock out/tag out isapplied to isolate equipment and prevent potential releases of productand energy to the surrounding environment as well as ensure the safetyof personnel.

Once all potential energy sources are locked out/tagged out, the tankcan be drained and made safe for human entrance.

During a lock out/tag out the monitors in the tank are actuallydisabled. Personnel monitor the other surrounding tanks for unexpectedchanges. Analyzing the tank level monitoring data by watching the level,volume and alarm data from the surrounding tanks, identifies tanks thatmay have an open pathway to either receive or transfer product to theequipment being locked out/tagged out.

FIG. 3 shows the tank level being drawn down (1) to a level that isacceptable for the Lock Out/Tag Out (LOTO) to be applied to the tank,and for maintenance work to being. Approximately 1 hour later the tanklevel beings to rise, indicating that the tank is not locked out. Whenthe second alarm was received, the terminal was contacted and determinedthat LOTO missed on one line, allowing product to flow to the tank.

Floating Roof Landings

The data received from the tank level monitoring system and the periodicinventory reconciliation system unexpectedly allow for operators toidentify floating roof landings at tank farms. The large storage tankshave floating roofs that float on the surface of the product containedwithin the tank. As the product level rises and falls, the roof risesand falls. These floating roofs have legs which can be set to be 3-4feet long (low) during operation phases but can be extended to be 5 or 6feet long (high) for maintenance purposes. When the tank needs to bemaintained, the legs are extended to the high setting, and the tank isdrained of product allowing the roof to rest on the floor of the tank.This allows for personnel to enter the tank for maintenance purposes. Ifthe legs are not set back to the low setting, and product is put in thetank, the legs will hit the bottom is tank is operated in a normalfashion as product exits that tank.

Accidental floating roof landings during operations often result inenvironmental incidents and potential mechanical damage to the floatingroof and the floor of the tank. Prior to this invention, alarms were setfor floating roof landings through the operation center. The alarmsfunction by comparing the current product level in the tank to anoperation selected level. This method of operation left a scenario inwhich floating roofs could land and remain undetected by operations. Forinstance, if the operation center sets the leg level on a floating roofto high legs using a low legs operation chart there is potential for thefloating roof to land on the floor of the tank with product remaining inthe tank. Previously, such a condition was discovered only during manualtank inspection and may continue for years unnoticed. Enough rooflandings will ultimately rupture the tank, resulting in severeenvironmental damage.

Referring now to FIG. 4, there are shown two locations where rooflandings are occurring. The first location had been set on high legs,while using the low legs setting, for at least 17 years. The secondlocation has been set on high legs, while suing the low legs settingsfor at least 15 years. Tanks generally are serviced and maintained onceevery twenty years. Therefore, if the roof legs are improperly set, rooflandings can occur for multiple years. As shown in FIG. 4, the two lowdata sets where the level fell below 6.5 feet, indicate a roof landing.

When the legs are set at high, the roof lands at the bottom of the tankwhen the volume drops. During tank operations, the operators areassuming the legs are in the low position and will often drop theoperational volume in the tank to just above the 3-4-foot level. In theinstances shown in FIG. 4, the tank level dropped to 4½ feet, the feetare set on high and roof landings occur right before the 4½ feet level.

Using the tank level monitoring and periodic inventor reconciliationdata, operators can detect potential roof landings. When roof landingsoccur, a pattern of alarms occur. Referring now to FIG. 5, the firstalarm will occur in tank level monitoring followed by an alarm inperiodic inventory reconciliation. These alarms occur as the tank levelenters and falls out of the critical zone for the tank.

The first alarm, occurring in tank level monitoring shows a normal truckloading, followed by a bounce in the tank level and volume, which bothcontinue to increase after loading completes, before finally settlingout at a level higher than the recorded levels at the end of the truckloading, causing an alarm to occur.

The second alarm occurs later as the tank volume continues to lower byloading and occurs when the tank level falls out of the critical zone.This alarm occurs within the product inventory reconciliation data andis caused by a discrepancy between the amount of product recorded asbeing loaded and the amount of product ordered.

FIG. 5 shows the tank complete loading of a truck at marker 1, at alevel of ˜6.25 feet, immediately followed by an increase in the tanklevel and volume. At marker 2, it can be seen that the rate of volumeincrease is slowing over time. The product level in the tank, combinedwith the shape of the curve indicates that the product is draining fromaround the internal floating roof of the tank, and then being accountedfor by floating level gauge. A call to the terminal was made, wheninvestigated, the confirmed the analysis in Tank Level Monitoring andPeriodic Inventory Reconciliation.

Tank Assignments and Inventory Control

When changing the tank line up at the rack, operations is required tomanually update the active tank assignment. Failure to do so may lead toinventory discrepancies, floating roof landings, environmentalregulations violations, and product becoming unavailable at the rack.

FIG. 6 shows a comparison of rack loading and ordering data to tank dataand results from the periodic inventory reconciliation. FIG. 7 showstank level decreasing due to loading, however, there is no associatedrack activity. FIG. 8 shows tank levels not decreasing however there isa large amount of rack loading activity. These three scenarios leadoperators to understand that tank conditions do not match up with rackmovements and ordering.

Operators can now check and find within 1 to 2 loading cycles if animproper tank was assigned to a specific truck. An alarm will sound froma given tank because the level is unexpectedly decreasing. Operators canrun a comparison with other tanks to see if those tanks are static. Thisallows the operations to reconcile product being loaded at the rack toensure that the correct product and tank is in fact active. Runningthese comparisons showing on the three read outs of FIGS. 6, 7 and 8 canshow the comparison between what was ordered at the rack to bedelivered, what tank it is coming from and what rack meters are active.

FIG. 7 shows tank level decreasing due to truck loading, with noassociated meter activity changes. This indicates that product shouldnot be going to the truck rack from this tank.

FIG. 8 shows the level of a second tank is not decreasing, despiterepeated requests to load trucks at the rack, as indicated by the meteractivity shown in the figure.

FIG. 9 shows that the invention can also detect when a valve isimproperly seated. As shown in FIG. 9, the tank level is slowingincreasing. This indicating that product is slowly entering the tankwhich indicates an improperly seated valve.

Pipeline Delay Detection

When receiving product from the pipeline delays may occur. The pipelineoperator may shutdown the product flow for any number of reasons. Whilepipeline operators are supposed to contact terminal operators, the sheernumber of terminals that reside on any given pipeline could result inhours before notice is received, if it is received at all. This canresult in many hours of wasted personnel time while the pipeline isdown. Further, there are operational risk associated with being inreceipt mode and having no product coming in from the pipeline. Further,a company with multiple terminals may manage product differently amongthe terminals if it knows in real-time that a pipeline has been shutdown. Therefore, there remains a need for a real-time detection system.

Using the tank level monitors and Periodic Inventory Reconciliation, aterminal operator can now monitor, and even alarm if desired, tanks thatare currently in receipt mode to ensure that product continues to flowinto the tanks and an expected rate. If this rate drops or ceases, analarm can be programmed to notify the operators that the pipeline hasshut down.

We claim:
 1. Automation and improvements to inventory reconciliation andtank level monitoring at tank farms, terminals and refineries haveprovided unexpected benefits for the identification of maintenance needsand policy violations that were previously unable to be identified, suchbenefits include: the identification of failing thermal relief valvesthat are unable to be tested due to location and product placement;visualizing tank alarm information with planned movement entries toprovide data that detects when product is misdirected through a failedthermal relief valve; and monitoring of the level and volume of tanks todetermine that product is being diverted to an improper location orunexpected location.
 2. The method of claim 1 wherein the tankmonitoring system indicates a slow continuous loss of product from atank over an extended period, indicating that a check valve for atransmix tank has failed; the failure of a check valve for a transmixtank allows product to flow to the oil waters separator from thetransmix tank; such flow is a reversal of a normal check valve operationwherein the check valve only allows water to flow from the oil waterseparator to the transmix tank.
 3. The method of claim 2 wherein thelevel of the transmix tank is continuously monitored to view increasingand decreasing changing levels that are improperly occurring over time.4. The method of claim 1 applied to the application of lock out/tag outisolation of equipment; wherein the tank level monitoring data fromtanks surrounding the locked out/tagged out tank identifies tanks thatmay have an open pathway to receive and transfer product to theequipment being locked out/tagged out.
 5. The method of claim 1 whereindata received from the tank level monitoring system and the periodicinventory reconciliation system is used to identify floating rooflandings at tank farms; wherein the floating roofs have legs that areshorter during operational phases and can be extended for maintenancephases; such a roof landing on the bottom of the tank triggering apattern of alarms; the first alarm occurring at tank level monitoringfollowed by a second alarm by the periodic inventory reconciliationsystem; the first alarm in tank level monitoring will sound as the tanklevel and volume continues to increase after loading completes, settlingout at a level higher than the recorded levels at the end of the truckloading; the second alarm in the inventory reconciliation data istriggered by a discrepancy between the amount of product recorded asbeing loaded and the amount of product being ordered; wherein the alarmsindicate that the product level in the tank, combined with the shape ofthe inventory reconciliation curve, indicates that product is drainingfrom around the internal floating roof of the tank.
 6. The method ofclaim 1 wherein rack loading and ordering data at tank farms arecompared, using data and results from periodic inventory reconciliation;such comparisons provide indications that an improper tank is beingloaded to a specific truck; wherein such comparisons between what wasordered at the rack and what is being delivered and what tank it iscoming from will prevent inventory discrepancies, floating rooflandings, and environmental regulation violations.
 7. The method ofclaim 1 wherein a terminal operator monitors and alarms tanks that arein receipt mode to ensure that product continues to flow into the tankat an expected rate; if the rate drops or seizes, an alarm is programmedto notify the operators that the pipeline is shutdown.